private Microsoft.Office.Interop.Excel.Application _objExcel;//Excel应用程序实例
private Microsoft.Office.Interop.Excel.Workbook _objBook;//当前操作的工作表
private Microsoft.Office.Interop.Excel.Worksheet _objSheet;//当前操作的表格
Microsoft.Office.Interop.Excel.Range range = _objSheet.UsedRange;
range.Insert(Microsoft.Office.Interop.Excel.XlDirection.xlDown, Missing.Value);

------解决方案--------------------
public static bool SaveDataTableToExcel(System.Data.DataTable excelTable, string filePath) //内存中的DataSet中的数据保存到excel中
       {
           Microsoft.Office.Interop.Excel.Application app = new Microsoft.Office.Interop.Excel.ApplicationClass();
           try
           {
               app.Visible = false;
               Workbook wBook = app.Workbooks.Add(true);
               Worksheet wSheet = wBook.Worksheets[1] as Worksheet;
               if (excelTable.Rows.Count > 0)
               {
                   int row = 0;
                   row = excelTable.Rows.Count;
                   int col = excelTable.Columns.Count;
                   for (int i = 0; i < row; i++)
                   {
                       for (int j = 0; j < col; j++)
                       {
                           string str = excelTable.Rows[i][j].ToString();
                           wSheet.Cells[i + 2, j + 1] = str;
                       }
                   }
               }
               int size = excelTable.Columns.Count;
               for (int i = 0; i < size; i++)
               {
                   wSheet.Cells[1, 1 + i] = excelTable.Columns[i].ColumnName;
               }
               app.DisplayAlerts = false;//设置禁止弹出保存和覆盖的询问提示框
               app.AlertBeforeOverwriting = false;//保存工作簿  
               wBook.Save();
               app.Save(filePath);//保存excel文件  
               app.SaveWorkspace(filePath);
               app.Quit();
               app = null;
               return true;
           }
           catch (Exception err)
           {
               MessageBox.Show("导出Excel出错！错误原因：" + err.Message, "提示信息",
               MessageBoxButtons.OK, MessageBoxIcon.Information);
               return false;
           }
           finally
           {
           }
       }


把内存中DataSet中的数据保存到excel文件中

------解决方案--------------------
[color=#0000FF][/color]文件上面加上
using Microsoft.Office.Interop.Excel;
using System.Data.OleDb;
当然需要添加引用；
首先新建一个Excel;
  string strConn = null;
 string strCommand = null;
  strConn = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + Server.MapPath("~/Upload/Excel.xls") + ";Extended Properties='Excel 4.0;HDR=yes;IMEX=2'";//找到excel的表格
 OleDbConnection conn = new OleDbConnection(strConn); //创建连接

   conn.Open(); //此时Excel 相当于一个数据库；打开数据库；

strCommand = "INSERT INTO [Sheet1$]( 姓名,性别) values ('张小亮','男')";
 OleDbCommand cmd = new OleDbCommand(strCommand, conn);
  cmd.ExecuteNonQuery();
  conn.Close();
注：完成对Excel 的操作，
发布后，该Excel 的权限要变为可写的，
该Excel 的表格
第一行  姓名，性别
Excel 操作时第一行的值代表的是列标题